Gemini Observatory: Exploring the Universe, Sharing its Wonders

Black Hole May Fuel Galactic Mass Exodus

March 11, 2010

For the latest information on this topic please see Durham University's recent press release titled: 'Catastrophic Event' Behind Halt of Star Birth in Early Galaxy Found."

Consequences of galaxy-scale outflows are profound in the early universe, and an international team led by David Alexander at Durham University (UK) provides insight into the process using new observations with the Gemini Near-Infrared Integral Field Spectrometer (NIFS) on Gemini North.

The material between galaxies is observed to be enriched in metals (elements more complex than helium) compared with primordial abundances, which requires early generations of star formation to produce the metals. The galactic outflows thought to be responsible for this enrichment must be extremely energetic for the material to escape a galaxy’s strong gravitational pull.

This recent work presents observations of a z = 2.07 quasar (SMM J1237+6203) that also emits strongly at submillimeter and infrared wavelengths. While the active nucleus is powerful (having an X-ray luminosity of about 1044 erg per second), the large submillimeter, radio, and infrared luminosities indicate that a luminous starburst is also present. The NIFS integral field unit data show spectrally broad [O III] emission that is correlated with the largest velocity offsets, which is characteristic of a galaxy-wide outflow. While the origin of the suggested outflow cannot be identified as either an AGN or starburst for certain, they persist over timescales appropriate for either process. The team concludes that the total energy of the outflow would be comparable to the binding energy of the galaxy spheroid, which, according Alexander, "...is literally at the point of blowing the galaxy apart."

Extended high-velocity emission has been observed in distant radio galaxies, but these galaxies are rare and therefore cannot provide a general explanation for the apparent feedback that occurs as galaxies evolve. The team has additional NIFS observations of other high-redshift, submillimeter-bright galaxies in hand, which they will use to provide a more systematic account of the radio quiet population. The current work will appear in Monthly Notices of the Royal Astronomical Society: “Revealing an Energetic Galaxy-Wide Outﬂow in a z ≈ 2 Ultraluminous Infrared Galaxy”, by David M. Alexander, A. Mark Swinbank (Durham University, UK), Ian Smail (Durham University, UK), Richard McDermid (Gemini Observatory), and Nicole P. H. Nesvadba (Université Paris).

Figure 2: [O III] intensity (left), narrow [O III] velocity map (middle), and line-free continuum image (right); circle in top right of velocity map denotes the seeing disk size. The contours represent an intensity weighted map of the broad [O III] emission components. The contour in the right panel traces the location and extent of the outflow at a scale of about 4-6 kiloparsecs. The numbered regions of the broad [O III] emission are plotted in Figure 3.

Figure 3: Velocity and FWHM components of the broad and narrow [OIII] emission plotted as a function of radius from the nucleus. The numbered regions correspond to those indicated in Figure 2.

The Gemini Observatory is an international collaboration with two identical 8-meter telescopes. The Frederick C. Gillett Gemini Telescope is located on Mauna Kea, Hawai'i (Gemini North) and the other telescope on Cerro Pachón in central Chile (Gemini South); together the twin telescopes provide full coverage over both hemispheres of the sky. The telescopes incorporate technologies that allow large, relatively thin mirrors, under active control, to collect and focus both visible and infrared radiation from space.

The Gemini Observatory provides the astronomical communities in six partner countries with state-of-the-art astronomical facilities that allocate observing time in proportion to each country's contribution. In addition to financial support, each country also contributes significant scientific and technical resources. The national research agencies that form the Gemini partnership include: the US National Science Foundation (NSF), the Canadian National Research Council (NRC), the Chilean Comisión Nacional de Investigación Cientifica y Tecnológica (CONICYT), the Australian Research Council (ARC), the Argentinean Ministerio de Ciencia, Tecnología e Innovación Productiva, and the Brazilian Ministério da Ciência, Tecnologia e Inovação. The observatory is managed by the Association of Universities for Research in Astronomy, Inc. (AURA) under a cooperative agreement with the NSF. The NSF also serves as the executive agency for the international partnership.